Data carrier device

ABSTRACT

A passive data carrier device ( 100 ) comprises an input port ( 110 ) for receiving a finite duration radio frequency input signal of defined time and frequency spectral characteristics. The data carrier device ( 100 ) comprises at least one branch ( 130 ) having combinations of passive RF elements, such as band filters ( 134 ) and time delays ( 136 ), optionally together with powder dividers ( 120 ) and combiners ( 140 ). The input signal is processed by the device ( 100 ) to form an output signal having time and frequency spectral characteristics different from the input signal. The data carrier device ( 100 ) has potential application in an RF identification system.

TECHNICAL FIELD

The present invention generally relates to a data carrier device, and inparticular to a passive data carrier device useful in a radio frequencyidentification tag.

BACKGROUND

A variety of technologies for storing data are available today withvarying scope of application depending upon their cost, memory capacityand method of data access. Examples of data storage techniquesassociated with computer industry are floppy diskette, compact disc andsemiconductor based memories.

Handling of manufactured goods and materials also require some form ofdata carrier device for their identification or surveillance from adistance. Their demand in terms of storage capacity is considerablylower than that required for computer industry. Two widely used methodsfor article identification and surveillance are printed opticalbar-codes and magnetic-strips. Bar-codes are commonly used foridentifying objects in shops and supermarkets. An application ofmagnetic strips is the credit card. The main reason for the popularityof bar-codes and magnetic strips is that they are inexpensive. Thedrawback of bar-codes and magnetic strips is that the reader has to havea physical contact or has to be very close, say a few centimeters, fromthe bar-code or magnetic strip to read. If there is no physical contact,then the space between the code and the reader should not have anyobstruction and properly aligned for correct readability. This requiresconcentration from the part of the human operator and therefore isinconvenient.

RFID (radio frequency identification) is another technology for articlesurveillance and identification. RFID enables larger readabilitydistance compared to that of the magnetic strip technology or thebar-code technology. The data is stored in an RFID system called RFIDtag which once interrogated by the remote reader, return an encodedradio signal that contains the data. Different embodiments of RFID tagsare disclosed, for example, in the following publications: U.S. Pat.Nos. 5,574,470; 5,625,341; 5,682,143; 5,995,006; 6,100,804; 6,346,884;6,424,263; and 6,441,740.

RFID-tag devices can be broadly divided based on the criterion whetherthey contain an integrated memory chip or not. Those that contain amemory chip, e.g. U.S. Pat. No. 5,874,902, in general have larger memorycapacity than those of chip-less tags, e.g. U.S. Pat. No. 6,708,881.However, chip based tags have a significantly higher cost compared tothat of the chip-less tags.

RFID-tags can also be divided based on the criterion whether theycontain a battery or not, denoted active and passive tags in the art. Ingeneral active tags, which are the most commonly available tags inmarket today, have a larger operational distance range when compared tothe passive tags, e.g. U.S. Pat. No. 6,621,417.

Passive chip-less data carrier devices used in RFID tags havesignificant advantages in that they are passive, of low cost and enablereadability at large distances. Furthermore, battery-free tags do nothave the problem of limited life time and the need for batteryexchanges.

The international application WO 2006/043876 discloses a passivechip-less data carrier device that comprises a powder divider havingmultiple output terminals connected to different branches. Each branchcomprises a unique set of a time delay, a phase shifter and anattenuator. The output terminals of the branches are then combined in apower combiner.

SUMMARY

The passive chip-less data carrier devices of WO 2006/043876 work reallywell with a finite radio frequency input signal of a given frequency andcan modulate the input signal in the time-domain to get, for each datacarrier device, a unique time-modulated output signal. However, thenumber of different data carrier devices that can uniquely respond to agiven input or mother signal is highly restricted. As a consequence, theprior art document WO 2006/043876 teaches the generation of a multitudeof child signals from the mother signal. Each such child signal can thenbe used as input signal to the data carrier devices.

The present invention overcomes these and other drawbacks of the priorart arrangements.

It is a general object of the present invention to provide a passivedata carrier device.

It is another object of the invention to provide a passive data carrierdevice that can implemented in a radiation frequency identification tag.

These and other objects are met by the invention as defined by theaccompanying patent claims.

Briefly, the present invention involves a passive data carrier devicecomprising at least one input port adapted for receiving a finiteduration radio frequency (RF) signal of defined time and frequencyspectral characteristics. M branches of the device have a respectiveinput terminal connected to one of the input ports and comprise passiveRF elements for processing the input signal. At least one output port isconnected to the branches and receives the processed output signal thathas time and frequency spectral characteristics different from the inputsignal.

According to the invention, each of the M branches comprises acombination of R_(k) band filters and S_(k) time delays, k=1 to M. Thenumbers R_(k), S_(k) are positive integers. Furthermore, at least one ofR_(k), S_(k) is larger than one if M is equal to one and R_(k), S_(k)are equal to or larger than one if M is a positive integer larger thanone.

The combination of the band filter(s) and time delay(s) is different fordifferent branches in the data carrier device, where the particularselection of band filters and time delays in the branches dictates themodulation in the time and frequency domain of the input signal to getthe processed output signal.

Thus, the data carrier device is realized as a combination of RF filtersand time delays resulting in a passive RF circuit. An input orenergizing signal enters a port in the data storage circuit and comesout through an output port of the data carrier device resulting in anoutput signal with spectral and time characteristics depending upon theparameters of the filters and time delays.

The device can have a combined input and output port by providing atermination at the output terminals of the M branches. This results in aone port data carrier device where the output signal is generated at theinput port. Here the time and spectral characteristics of the outputsignal is determined by the parameters of the time delays, filters andthe termination. Therefore, different characteristics of delays, filtersand terminations result in different output signals from the datacarrier device. If we have the capability of generating N differentsignals using the characteristics of filters, time delays andterminations, the data carrier device will have a data carrying capacityof log₂N bits.

The data carrier device can be connected to one or more antennas of anantenna system to be capable of receiving and radiating processedsignal. The data carrier device when connected with antennas can be usedas a radio frequency identification tag. A remote device capable ofreceiving and interpreting the output signals from the said data carrierdevice as bits can then be used as reader or interrogator of the RFIDtag.

The invention offers the following advantages:

-   -   Can be implemented using only passive RF components;    -   Does not require a dedicated power source or battery;    -   Provides a chip-less implementation of data carrier device;    -   Processes an input signal both in the time and frequency domain;        and    -   Can generate a vast amount of RFID tag addresses from a single        interrogation signal.

Other advantages offered by the present invention will be appreciatedupon reading the below description of the embodiments of the invention.

SHORT DESCRIPTION OF THE DRAWINGS

The invention together with further objects and advantages thereof, maybest be understood by making reference to the following descriptiontaken together with the accompanying drawings, in which:

FIG. 1 illustrates an embodiment of a branch useful in a data carrierdevice according to the present invention;

FIG. 2 illustrates an embodiment of a data carrier device according tothe present invention with separate input and output ports.

FIG. 3 illustrates an embodiment of a data carrier device according tothe present invention with multiple terminations to form a combinedinput and output port;

FIG. 4 illustrates an embodiment of a data carrier device according tothe present invention with a single termination to form a combined inputand output port;

FIG. 5 illustrates the data carrier device of FIG. 3 equipped with areceiving and transmitting antenna for use in a radio frequencyidentification tag;

FIG. 6 illustrates a data carrier device equipped with multiplereceiving and transmitting antennas for use in a radio frequencyidentification tag;

FIG. 7 illustrates a radio frequency identification tag according to thepresent invention in communication with a radio frequency identificationreader; and

FIG. 8 illustrates how the responses of the data carrier devices will bedecoded using their energy distribution in both the frequency and timedomain.

DETAILED DESCRIPTION

Throughout the drawings, the same reference characters will be used forcorresponding or similar elements.

The present invention generally relates to a passive, chip-less datacarrier device that may be used in radio frequency identification (RFID)tags for generating, based on the reception of an input signal, anoutput signal processed in the time and frequency domain for the purposeof generating an output signal that can be used as unique address signalfor the RFID tag.

The passive data carrier device of the invention comprises at least oneinput port adapted for receiving a finite duration radio frequency (RF)input signal of defined time and frequency spectral characteristics. Thedevice also comprises M branches that each has an input terminalconnected to one of the at least one input ports and an output terminalconnected to an output port, which can be the same or different from theinput port. A branch comprises passive RF elements for processing theinput signal to form an output signal at the output port(s) that, due tothe branch processing, has time and frequency spectral characteristicsdifferent from the input signal. This means that the data carrier deviceof the present invention includes passive RF elements that are able tomodulate a RF signal both in the time and frequency domain to generatean encoded RF signal.

According to the invention, the input signal is a finite duration RFsignal of defined time and frequency spectral characteristics. A binaryon-off keyed waveform of a given (frequency) bandwidth, for instance asinusoidal wave of fixed duration when ON and zero signal when OFF is anexample of a useful. RF input signal. Different data carrier devices ofthe invention can be useful for different bandwidth intervals. As aconsequence, a set of finite duration RF signals of different time andfrequency characteristics can be available and used in connection withdifferent carrier devices. The RF input signal can be generated locallyor can be made available remotely through a wired connection orpreferably through antennas wireless from a remote point and can beconveniently called the energizing signal for the data carrier device.

The invention is particularly adapted for usage in connection with highfrequency RF signals, in which the RF input signal has a bandwidth inthe GHz range. The invention is though not limited to this particularfrequency band.

The invention teaches that the data carrier device comprises M branches,where each of the branches comprises a combination of R_(k) band filtersand S_(k) time delays, preferably in the form of N_(k) pairs of bandfilters and time delays. In a particular embodiment, each such pair in abranch is unique for that branch in that it contains a combination ofband filter and time delay that no other pair of that branch contains.This, though, means that another pair of the branch can then have thesame band filter (time delay) but then has a) different associated timedelay (band filter).

According to the invention, R_(k), S_(k), N_(k) are positive integers.Furthermore, at least one of R_(k), S_(k) is larger than one if M isequal to one and R_(k), S_(k) are equal to or larger than one if M is apositive integer larger than one. Similarly, if M is equal to one N_(k)is larger than one and if M is a positive integer larger than one, thenN_(k) is equal to or larger than one.

In other words, the data carrier device can include a single branch butthen that single branch comprises at least two band filters and at leastone time delay or at least one band filter and at least two time delays.If the device on the other hand contains at least two branches, eachbranch can contain a unique combination of at least one band filter andtime delay, although in a preferred embodiment, they contain more thanone pairs. It is also anticipated by the present invention that thebranches in a multi-branch implementation do not necessarily have tocontain the same number of band filters and time delays. The importantfeature is instead that the combination of the R_(k) band filters andS_(k) time delays is different for different branches of the M branches.Due to the inclusion of these different combinations of band filters andtime delays, a resulting processed output RF signal will have time andfrequency spectral characteristics different from the input signal(energizing signal).

It is anticipated by the present invention that a time delay can be fromzero seconds, i.e. basically zero delay, and above.

FIG. 1 illustrates the functional blocks and their interconnectioncircuit in a branch 130 in a preferred embodiment of the data carrier.The branch 130 has an input terminal 131 and an output terminal 133.Between these terminals 131, 133 there is a combination of pairs 132 ofband filters 134 and time delays 136. Each pair 132 in a give branch 130is preferably unique compared to other filter-time delay pairs 132 inthe same branch 130. This means that comparing two such pairs 132 in abranch 130 they contain different band filters 134 and/or different timedelays 136. However, a same band filter 134 may occur at least twice ina branch 130 for increasing the sharpness of the responses.

The branch k 130 comprises a combination of N_(k) pairs 132 of bandfilters 134 and time delays 136, where k=1 to M. The number N_(k) is apositive integer equal to or larger, preferably larger, than one.However, for single branch devices, the number N₁ (k=1) is a positiveinteger equal to or larger than two.

In those cases M is a positive integer larger than one, the differentnumbers N_(k) may all be the same or different for different k:s.

The band filter (BF) 134 can either be a band pass filter or band rejectfilter. In the figure, each band filter 134 is followed by a time delay(TD) 136. In an alternative implementation, each time delay 136 isfollowed by a band filter 134. In alternative embodiments, the branch130 does not have to contain pairs 132 of band filters 134 and timedelays 136, i.e. R_(k)·S_(k) but instead R_(k)>S_(k) or R_(k)<S_(k).

As illustrated in FIG. 1, the k^(th) branch 130 consists of N_(k) bandfilters 134 and N_(k) time delays 136. Part of the input high frequencysignal entering the input terminal P_(k) 131 of the branch 130 will besubjected to reflection and the remaining portion of the signal leavesthe output port Q_(k) 133 of the branch 130. The reflection at portP_(k) 131 and transmission of the signal through port Q_(k) 133 aremeasurable and can be characterized in terms of its input reflectioncoefficient and transmission coefficient. Those skilled in the art ofband filters and time delays can appreciate therefore that thecharacteristics of the reflected signal at port P_(k) 131 and thetransmitted signal at port Q_(k) 133 in terms of its amplitude and phasein relation to frequency and time will depend upon the design parameterschosen for designing the band filters 134 and time delays 136.

FIG. 2 illustrates an embodiment of a data carrier device 100 accordingto the present invention. The input signal enters an input port A 110that is connected to an input terminal 121 of a powder divider 120. Thedivider 120 divides the input signal by means of an M-way power divisioninto M branch signals. The divider 121 therefore comprises M outputterminals 123, each being connected to a respective input terminal 131of the M branches 130. Each branch 130 can be as illustrated in FIG. 1.

The output terminals 133 of the branches 130 are connected to respectiveinput terminals 141 of a power combiner 140. As a consequence, theoutput signals from the M branches 130 are combined by means of a powercombiner 140 to form an output signal that is forwarded from an outputterminal 143 of the combiner 140 to the output port B 150.

The reflected signal at port A 110 and the transmitted signal at port B150 in terms of their amplitude and phase in relation to frequency andtime will depend upon the design parameters chosen for designing theband filters, time delays, power combiner and power dividers.

As in quadrature phase shift modulation (QPSK) where four differentphases of a signal result in a bit capacity of log₂4=2 bits, thecapability of generating N signals of different properties of the signalat port B of the data carrier device 100 using the combination offilters and time delays for the data carrier device result in a datacarrying capacity of log₂N bits.

FIG. 2 illustrates a data carrier device 100 with a separate input portA 110 and a separate output port B 150. FIGS. 3 and 4 illustrateone-port embodiments having a single port A 110 functioning both asinput and output port.

In FIG. 3 the output terminals 133 of the M branches 130 are connectedto respective input terminals 161 of M terminations or terminators 160.In this case, only the reflected signals will reach the combined inputand output port A 110. The divider 120 in FIG. 3 will then both havepower dividing and combining properties. An example of a suitable suchdivider/combiner is the Wilkinson's divider/combiner.

In FIG. 4 a single termination 160 is instead used by connecting theoutput terminal 143 of the power combiner 140 to the input terminal 161of the single termination 160. The discussion above regarding combineddividing/combining functionality applies mutatis mutandis to this datacarrier device embodiment 100.

The termination 160 can be realized as a time delay, an energydissipater, an energy absorber, an open circuit, or as a short circuit.Therefore the capability of generating N signals of different propertiesat port A 110 of the data carrier device 100 in FIGS. 3 and 4 can beachieved through selection of or by varying the specifications offilters, time delays and terminations 160 in each branch 130. Thisresult in a data carrying capacity of log₂N bits for the data carrierdevice 100.

FIG. 5 illustrates an embodiment in which a receiving and transmittingantenna 170 is connected to port A 110 of the data carrier device 100illustrated in FIG. 4. The antenna 170 then captures an input orenergizing signal from a remote reader/interrogator. The input signal isthen processed by the carrier device 100 to form a reflected outputsignal with different time and frequency characteristics than the inputsignal. This output signal is then transmitted by the antenna 170 andcan be received by the reader/interrogator.

FIG. 6 illustrates a data carrier device 100 where each individualbranch 130 is connected to a separate combined input and output port 110and each port 110 has a dedicated receiving and transmitting antenna170.

In both FIGS. 5 and 6, the received energizing signal enters thebranches 130 of the data carrier device 100 via the antenna(s) 170. Onthe other hand, the antenna signal is provided by radiation from aremote point. In these embodiments, the capability of tuning theindividual branch parameters such as the filter properties, time delayproperties and terminations to obtain N different reflected signals fromthe antenna(s) 170 implies that the device 100 has a data carryingcapability of log₂N bits. Therefore, FIGS. 5 and 6 embody the capabilityof the data carrier device 100 together with antenna(s) 170 as a part ofa RF identification/authentication system once it is energized by RFsignal(s).

In FIGS. 5 and 6, the antenna(s) 170 has (have) been used both forreceiving a RF input signal and for transmitting a RF output signal. Thepresent invention can though instead utilize dedicated receivingantenna(s) and dedicated output antenna(s). For instance, a receivingantenna can be connected to the input port A 110 of FIG. 3 and anothertransmitting antenna is then connected to the output port B 150.

It is anticipated by the present invention that the teachings of thedifferent embodiment described above and disclosed in the drawing can becombined to get new embodiments of the data carrier device of thepresent invention. Also such embodiments are encompassed in the scope ofthe invention.

A RF identification/authentication system for reading information storedin a RF tag 1 comprising at least one antenna 170 or antenna systemconnected to a data carrier device/system 100 of the present inventionis illustrated in FIG. 7. FIG. 7 only shows the functional relationshipsbetween the entities, rather than any physical connections and/orphysical relationships. The system in FIG. 7 includes a wireless RFtransmitter 10 having a transmitting antenna 15 capable of sendingelectromagnetic radiations to the RF tag system 1. A receiver 20 withconnected receiving antenna 25 is capable of detecting the radiationsfrom RF tag system 1. The transmitter 10 and receiver 20 with theirantennas 15, 25 can be housed in a single reader/interrogator device,schematically denoted with the reference number 2 in the figure.

The RF tag 1 can of course contain more than one passive data carrierdevice 100 according to the present invention. In such a case, each datacarrier device 100 preferably has a dedicated antenna or antenna system170.

The present invention has, due to the modulation in both the frequencyand time domain, the capability of generating a vast amount of differentoutput signals for a single input signal with given time duration andbandwidth. As a consequence, a single input signal can be used asinterrogation signal for a vast amount of different RFID tags that eachcomprises a data carrier device of the invention but with differentcombinations of band filters and time delays.

As an example, assume a RFID tag design as illustrated in FIG. 5.Further assume that we have five different band reject filters BF_(i)and five different time delays TD_(i), i=1 to 5, available for usage inthe data carrier device of the RFID tag. Also assume that each devicecomprises three branches (M=3) and that each branch comprises threepairs of filters and time delays (N_(k)=3, k=1 to 3) selected from theset of five band rejection filters and five time delays.

There are 3600 different combinations of band reject filters and timedelays that can be used for the first branch if each filter-time delaypair is unique. If the same combination cannot be used for the secondand third branch, we have 3599 combinations for the second branch and3598 combinations for the third branch. Taken together we have thepotential of generating about 4.6×10¹⁰ different output signals given asingle input signal having bandwidth covering the rejection frequenciesof the five band reject filters. We have therefore the potential ofgetting 4.6×10¹⁰ different tag addresses from a single input signal byutilizing different combinations of the five filters and the five timedelays.

The response of the data carrier device according to the presentinvention is a signal that will be decoded using their amplitudedistribution in both frequency and time domain. FIGS. 8A and 8Billustrate two such response examples from two different data carrierdevices from a frequency-time perspective. As can be seen from thefigures, the frequencies at different times are different between thesesignals and this difference can be the basis for classifying or decodingdifferent data. Therefore, different such frequency-time-amplituderelationships of the responses can be interpreted as different codesencoded in the data carrier device. As in quadrature phase shiftmodulation (QPSK) where four different phases of a signal result in abit capacity of log₂4=2 bits, the capability of generating methodicallyN different signals with different frequency-time-amplituderelationships for the data carrier device result in a data carryingcapacity of log₂N bits.

It will be understood by a person skilled in the art that variousmodifications and changes may be made to the present invention withoutdeparture from the scope thereof, which is defined by the appendedclaims.

The invention claimed is:
 1. A passive data carrier device comprising:at least one input port adapted for receiving a finite duration radiofrequency (“RF”) input signal of defined time and frequency spectralcharacteristics; M branches, each having an input terminal connected toan input port of said at least one input port and comprising passive RFelements for processing said input signal; and at least one output port,each being connected to a branch of said M branches, wherein each ofsaid M branches comprises a combination of R_(k) RF band filters andS_(k) RF time delays, k=1 to M, where R_(k), S_(k) are positive integersand at least one of R_(k) and S_(k) is larger than one if M is equal toone and both R_(k) and S_(k) are equal to or larger than one if M is apositive integer larger than one, the combination of said R_(k) RF bandfilters and S_(k) RF time delays being different for different branchesof said M branches, and a processed RF output signal at said at leastone output port has time and frequency spectral characteristicsdifferent from said RF input signal.
 2. The device according to claim 1,wherein each of said M branches comprises a combination of N_(k) pairsof a RF band filter and a RF time delay, k=1 to M, where N_(k) is apositive integer larger than one if M is equal to one and N_(k) is apositive integer equal to or larger than one if M is a positive integerlarger than one.
 3. The device according to claim 2, wherein M is apositive integer larger than one.
 4. The device according to claim 2,wherein R_(k), S_(k) are positive integers larger than one.
 5. Thedevice according to claim 1, wherein M is a positive integer larger thanone.
 6. The device according to claim 5, further comprising a RF powerdivider having an input terminal connected to said at least one inputport and having M output terminals, where each output terminal isconnected to the input terminal of a respective branch of said Mbranches.
 7. The device according to claim 6, further comprising a RFpower combiner having M input terminals, where each input terminal isconnected to an output terminal of a respective branch of said Mbranches, and an output terminal connected to said at least one outputport.
 8. The device according to claim 6, further comprising a RF powercombiner having M input terminals, where each input terminal isconnected to an output terminal of a respective branch of said Mbranches, and an output terminal connected to a termination.
 9. Thedevice according to claim 6, further comprising M terminations, whereeach termination is connected to an output terminal of a respectivebranch of said M branches.
 10. The device according to claim 5, furthercomprising a RF power combiner having M input terminals, where eachinput terminal is connected to an output terminal of a respective branchof said M branches, and an output terminal connected to said at leastone output port.
 11. The device according to claim 5, further comprisinga RF power combiner having M input terminals, where each input terminalis connected to an output terminal of a respective branch of said Mbranches, and an output terminal connected to a termination.
 12. Thedevice according to claim 11, wherein said termination is selected froma group consisting of: an energy dissipater; an energy absorber; an opencircuit; and a short circuit.
 13. The device according to claim 5,further comprising M terminations, where each termination is connectedto an output terminal of a respective branch of said M branches.
 14. Thedevice according to claim 13, wherein said termination is selected froma group consisting of: an energy dissipater; an energy absorber; an opencircuit; and a short circuit.
 15. The device according to claim 1,wherein R_(k), S_(k) are positive integers larger than one.
 16. Thedevice according to claim 1, wherein said RF band filters are selectedfrom a group consisting of: a RF band pass filter; and a RF band rejectfilter.
 17. The device according to claim 1, wherein said input portbeing a combined input and output port.
 18. A radio frequencyidentification tag comprising: at least one passive data carrier deviceaccording to claim 1; and at least one antenna connected to said atleast one passive data carrier device.
 19. The identification tagaccording to claim 18, wherein each antenna of said at least one antennais connected to a respective combined input and output port of said atleast one passive data carrier device.
 20. The identification tagaccording to claim 18, wherein said at least one antenna is an antennasystem comprising: at least one receiving antenna, where each receivingantenna is connected to a respective input port of said at least onepassive data carrier device; and at least one transmitting antenna,where each transmitting antenna is connected to a respective output portof said at least one passive data carrier device.
 21. The deviceaccording to claim 1, wherein said M branches are free of any active RFelements.